NEFL and amyotrophic lateral sclerosis: Both CSF p‐NfH and NfL levels were significantly different in ALS compared with Not‐deg (0.538 ng/mL, P < .0001, and 1300.45 pg/mL, P < .0001, respectively), whereas only CSF p‐NfH levels were significantly increased in ALS versus Deg (1.413, P = .019).